FORT HOOD — A soldier shot and killed four people, including himself, and injured 16 at the Fort Hood military base, located outside of Killeen, on Wednesday afternoon. The casualties mark the second mass shooting at Fort Hood in five years.

Nine patients are in treatment in the intensive care unit at the Scott & White Hospital in Temple. Three were in critical condition Wednesday night, according to Deontrea Jones, a hospital spokesman.

The soldier, who was identified by U.S. Rep. Michael McCaul, R-Austin, as 34-year-old Ivan Lopez, suffered from “unresolved” mental and behavior health issues and was in treatment, according to Lt. Gen. Mark Milley. Fort Hood officials said they would not confirm Lopez was the shooter.

According to Fort Hood officials, the shooter fired at individuals in the 1st Medical Brigade area of Fort Hood a little after 4 p.m. He died of self-inflicted injuries after a military police officer approached him.

Milley said though the shooter had not been formally diagnosed, he was undergoing the diagnosis process for post-traumatic stress disorder. The shooter served in Iraq for four months in 2011 and had a wife and children who lived near the base.

“That’s a lengthy diagnosis,” Milley said.

Ben Armstrong, director of UT’s Student Veteran Services, said many veterans at UT have served at Fort Hood or have other close connections with the base, although there is no way of tracking an exact number. Armstrong said he and other members of Student Veteran Services have not yet decided on a course of action or support plan.

“The immediate thing we’re worried about is the families and soldiers that are on base,” Armstrong said. “Right now I think that all we can do is hope and pray for the people that are on base, and we can go from there once we figure out what the realities of the situation are.”

In 2009, Nidal Malik Hasan, a U.S. Army major and psychiatrist, shot and killed 13 people and injured more than 30 others at Fort Hood. In 2010, former Secretary of Defense Robert Gates ordered the military to better identify potential workplace violence, improve information sharing between agencies and review emergency response capabilities at installations.

At a press conference in Chicago, President Barack Obama expressed grief and frustration that another shooting happened on a military base.

“Our thoughts and prayers are with the entire community, and we’re going to do everything we can to make sure Fort Hood has what it needs,” Obama said. “Folks there sacrifice so much on behalf of our freedom. … They serve with valor and distinction. When they’re at their home base, they need to feel safe. We don’t know what happened tonight, but obviously that sense of safety has been broken again.”

Sociology sophomore Sara Tracy, who attended UT as a freshman and will be returning in the fall, lives in Killeen just a few miles away from the Fort Hood base and has family and friends who work there.

Tracy said she still has vivid memories from the 2009 shooting, which happened when she was a junior in high school.

“The first time this happened, we couldn’t leave school,” Tracy said. “It was just scary, because a lot of my friends couldn’t get ahold of their parents because the cell service is terrible when a lot of people use their phones. People were worried because they have parents who work there, and it’s just like the same thing all over again.”

Tracy said the whole community is affected by the shootings.

“It’s emotional — earlier I just cried,” Tracy said. “You just don’t expect it to happen again … you want everybody to be safe.”

Veteran John Daywalt, a government junior from Killeen whose father still works at the Fort Hood base, said another shooting at the base was not something he expected to happen.

“Hearing that it happened a second time is even more devastating,” Daywalt said. “I just hope that the families are all OK and they get the proper respect that they deserve. It just kind of hits you by surprise.”

Daywalt, who served as a paratrooper in Afghanistan, said gun regulation on army bases is more stringent than people realize.

“I think there’s definitely a misconception that everyone on base is always carrying a weapon,” Daywalt said. “You think that just because they’re in the military, they’re always carrying a weapon. In reality, you are not allowed to touch a weapon without specific orders … so it’s not like if there was something like that you would be able to just respond immediately.”